3,3,3- 1Department of Aerospace Engineering, University of León, 24071 León, Spain (alberto.escapa@unileon.es)
- 2Department of Applied Sciences, University Centre of Defence at the Spanish Air Force Academy, 30720 Santiago de la Ribera, Spain
- 3VLBI Analysis Center (UAVAC), Department of Applied Mathematics and Aerospace Engineering, University of Alicante, 03690 Alicante, Spain
The main part of the precession/nutation of the Earth is due to its gravitational interaction with the Moon and the Sun. Such interaction can be characterized by the Earth geopotential that depends on the orbital ephemerides of the Moon and the Sun. In turn, the ephemerides can be expressed in terms of the so-called fundamental arguments that comprise: the mean anomaly of the Moon (l); the mean anomaly of the Sun (l’); the mean argument of latitude of the Moon (F); the mean elongation of the Moon from the Sun (D); and the mean longitude of the Moon’s mean ascending node (Ω) —to shorten, Delaunay arguments.
Common theoretical developments, for example, those based on the Hamiltonian formalism (e.g., Kinoshita 1977 or Escapa et al. 2017), or practical evaluation of the nutation series (e.g., IERS Conventions 2010, sec 5.7.1) assume that Delaunay arguments can be approximated as linear in time. However, strictly speaking this is not the case (e.g., Simon et al. 1994), the arguments being polynomials in time of fourth degree.
In view of the current demands on Earth rotation determination (about 1mm on the Earth surface); the guidelines of IAG 2019 and IAU 2021 resolutions; and the terms of reference of the IAU / IAG Joint Working Group on Consistent Improvement of the Earth rotation Theory (CIERT), it is necessary to assess the accuracy of such approximation both because the mandatory consistent development of the models, and also because its potential numerical relevance.
In this communication, within the Hamiltonian framework, we will derive the contributions to the nutations due to the non-linear time evolution of Delaunay arguments, comparing them with the common linear case. We will also discuss the practical implications from the point of view of the standards and the operational use of the nutation series.
Acknowledgments.- This work has been partially supported by the Spanish projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación and SEJIGENT/2021/001 funded by Generalitat Valenciana.
How to cite: Escapa, A., Baenas, T., Karbon, M., Belda, S., and Ferrándiz, J. M.: Contribution of the non-linear time evolution of Delaunay arguments to the Earth nutation series, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14096, https://doi.org/10.5194/egusphere-egu26-14096, 2026.
